Optical networks continue to grow as network usage continues to evolve. To date, optical networks utilize optical spectrum in the C-band (e.g., about 1527 nm to 1567 nm) with Erbium Doped Fiber Amplifiers (EDFAs). There have been plans and projections to extend the usage of optical spectrum to other bands such as the L-band (e.g., 1569 nm to 1611 nm), but such approaches have not been widely deployed. Conventional C+L band approaches (or planned approaches) treat each band as a separate entity. Initially, only C-Band hardware is deployed with the idea later that, when the optical spectrum in the C-Band is exhausted (either through use or channel block), the L-Band hardware would be added. Again, there are systems deployed with the ability to add the L-Band hardware, but this simply has not occurred for various reasons. As described herein, the C-Band hardware and the L-Band hardware can include multiplexing/demultiplexing components, amplifiers, Optical Channel Monitors (OCMs), and optical modems. One particular problem with later adding the L-Band hardware is a pronounced performance shift between existing C-Band channels as the new L-Band signals appear due to Stimulated Raman Scattering (SRS).
FIG. 1 illustrates a graph 10 of optical spectrum with only C-Band channels deployed compared with a graph 12 of the optical spectrum illustrating the effect of SRS as the L-Band channels are populated. As seen in the graphs 10, 12, there is a pronounced performance shift in existing C-Band channels as L-Band channels are populated. As a consequence, an optical system would need to adjust a number of operating parameters in order to rebalance the C-Band channels as the L-Band channels are populated. The C-Band channels also need to be engineered with enough margin at the beginning of life to absorb the eventual penalty associated with L-Band usage. Failing to do this properly could result in existing signals seeing traffic hits due to expansion in the L-Band. For Raman amplification, it is also very difficult to accurately calibrate Raman gain in the C-Band for the eventual effect of the L-Band channels and L-Band Raman amplification.
A conventional approach to addressing these limitations is noise loading where unfilled channels are replaced by noise, such as generated by an Amplified Spontaneous Emission (ASE) source. This approach is done within a single band, i.e., the C-Band, and has not been suggested between different bands, in a coordinated manner.